The present invention is an improvement within a Fluid Pressure Assisted Rotary Shaft Seal With Labyrinth Bushing and Replacement Seal Sleeve Cartridge of U.S. Pat. No. 4,482,194 issued on Nov. 13, 1984, and assigned to the common assignee. The rotary shaft seal of that patent seals a shaft supported for rotation about its axis within a housing bore by an anti-friction bearing interposed between the shaft and the housing bore. The anti-friction bearing has an outer bearing race fixed to the housing and an inner bearing housing fixed to the shaft and rotating therewith. The seal assembly includes an annular bushing fixed to the shaft adjacent the anti-friction bearing and on the high pressure side of the housing. The seal assembly further includes an annular static seal race operatively fixed to the housing and having axially opposed end faces. An annular rotating seal race is operatively coupled to the shaft and has an end face in sealable contact with one opposing end face of the static seal race. A replaceable wear sleeve cartridge is sealably fixedly mounted to the housing bore. The annular labyrinth preseal bushing fixed to the shaft defines a labyrinth preseal between the labyrinth preseal bushing and the replaceable wear sleeve cartridge.
A compressed seal wedge resiliently couples the end face of the rotating seal race opposite that in abutment with the annular static seal race, to the presealed bushing. The seal wedge, which is preferably of diamond shaped cross-sectional configuration, has opposite axial ends compressably received within facing aligned V-shaped grooves within opposed faces of the bushing and the rotating seal race. The seal wedge which is preferably formed of an elastomeric material provides a biasing force to the annular rotating seal race to produce the correct closing force between the abutting seal race and faces. The seal wedge acts further as a non-clogging elastomeric drive spring while preventing liquid and foreign material from entering the interior of the housing at the gap between the rotating seal race and the bushing which supports the same. To ensure a positive fluid seal downstream of the labyrinth preseal, O-rings are incorporated between the replaceable wear sleeve cartridge and the housing, between the labyrinth preseal bushing and the rotating annular seal race and between the static seal race and the wear sleeve cartridge.
While the seal as set forth in U.S. Pat. No. 4,482,194 has proved to be very reliable in low pressure, low speed, sewage applications when incorporated in a comminutor, when such a comminutor is employed in paper and pulp processing at higher speed and higher applied pressure across the seal, relatively extreme seal face pressure occurs, resulting in deflection of the rotating and static faces, loss of seal at the interface, pitting and fraction of the rotating and static races at the interface as well as increased friction and high energy consumption during comminutor operation. Additionally, some loss of seal is experienced across the seal wedge and the seal wedge is subject to configurational distortions under the high pressure experienced by the seal wedge which tends to produce a set within the elastomeric material.
It is, therefore, a primary object of the invention to provide an improved rotary shaft seal of this type having extended seal life for the seal faces due to reduced friction therebetween, a reduction in energy consumption due to decreased drag on the seal faces, increased seal across the seal wedge, increased tolerance allowable for the race dimensions and retention of seal face contact under high shaft deflection.